Co-injection nozzle for an injection moulding device for producing multi-layered injection-moulded products

ABSTRACT

A co-injection nozzle for an injection moulding device for producing multi-layered injection-moulded products. The nozzle includes: a central bore; a valve needle for opening and closing a nozzle opening; an annular inner melt channel for the first melt; an annular central melt channel for a second melt; and an annular outer melt channel for the first melt, the inner, central and outer melt channels being fluidically combined in the nozzle tip to form a concentrically-layered melt stream. The nozzle further includes a nozzle body and a melt runner insert having the central bore of the nozzle. The melt runner insert has a circular cylindrical section, by which the insert is held in a central bore of the nozzle body. At least one distribution channel for the first melt and at least one distribution channel for the second melt are formed in the outer surface of the circular cylindrical section, with the distribution channels running substantially in the axial direction.

TECHNICAL FIELD

The invention relates to a co-injection nozzle for a hot runnerco-injection device of an injection moulding apparatus for theproduction of multilayer injection moulded products, in particularinjection moulded products with a barrier or sealing layer. Co-injectionnozzles of this type comprise an annular inner melt channel which, inthe downstream half of the co-injection nozzle, is formed by the centralbore and the valve needle and is in fluid communication with a firstmelt supply channel; an annular middle melt channel which is in fluidcommunication with a second melt supply channel and which extends aboutthe annular inner melt channel; and an annular outer melt channel whichis in fluid communication with the first melt supply channel and whichextends about the annular middle melt channel. The inner, middle andouter melt channels are fluidically merged in the region of the nozzletip in order to form a concentrically layered melt stream.

TECHNICAL BACKGROUND

Co-injection nozzles or hot runner co-injection devices for injectionmoulding apparatus, with which two different melts can be simultaneouslyinjected through a nozzle orifice into a moulding chamber or cavity ofan injection mould, have been known for a long time (for example U.S.Pat. No. 4,657,496). Most older co-injection nozzles have two separatechannels for the two melts, which are disposed in a manner such that atwo-layered stream of melt is discharged from the nozzle orifice.

For the production of multilayer injection moulded products, inparticular protective containers for foodstuffs, pharmaceuticalproducts, blood samples, etc., with what is known as a barrier orsealing layer, a special type of co-injection nozzle is actually used inwhich the outflow stream is triple-layered and concentricallyconfigured, wherein the barrier layer forms the middle layer.

WO 81/00231 discloses a co-injection nozzle of this type, which combinesthree separate melt streams in one triple-layered, concentric meltoutflow stream. In that nozzle, the inner melt stream can be regulatedusing a valve needle disposed in a central bore of the nozzle.

In other co-injection nozzles of this basic type, a first melt isdivided into two streams outside or inside the co-injection nozzle whichthen form an inner and outer layer of the concentric outflow stream. Asecond melt is guided between the two layers and forms the middlebarrier layer. The three layers are then combined into a multilayer meltstream outside or inside the co-injection nozzle and then injected intothe mould cavity as a concentric outflow stream, whereupon a multilayerinjection moulded product is formed with a barrier layer that is coveredon both sides. The melts of the various layers can be regulated as afunction of the type of embodiment of the co-injection nozzle or theco-injection device. In order to enclose the barrier layer completely inthe melt for the outer and inner layer, at the respective start and endof an injection moulding procedure, only the melt for the outer and/orthe inner layer is injected, without the melt for the middle layer.

EP 0 929 390 discloses a co-injection nozzle in which the three meltlayers are combined in a combination unit disposed upstream of thenozzle and then guided along an elongate tubular flow channel to thenozzle orifice. The tubular flow channel is formed by a central bore inthe nozzle body and a valve needle disposed therein. The valve needlecan be used to adjust the flow of the inner melt layer in thecombination unit. In addition, the flow of the individual melt streamsis regulated via the supply unit.

EP 0 911 134 describes a co-injection unit in which three melt streamsare guided through a respective melt supply opening into theco-injection nozzle and are combined to form a concentrically layeredmelt stream in the nozzle tip region shortly before the nozzle orifice.The melt for the inner layer is guided in an annular inner melt channelwhich is formed by a central bore and a valve needle. The melt for themiddle layer is guided in an annular middle melt channel which extendsabout the annular inner melt channel. The melt for the outer layer isguided in an annular outer melt channel which extends about the annularmiddle melt channel. The inner and middle melt channels can be closedoff by the valve needle while the outer melt channel remains open.

WO 00/54955 discloses a co-injection nozzle in which the two melts forthe inner and middle layer are combined in a first upstream combinationunit outside the co-injection nozzle and then guided together along aninner central melt channel to the nozzle orifice in order to obtain acombined melt stream which is as stable as possible. In the region ofthe nozzle tip, the melt for the outer layer is combined with thealready combined central melt stream and then injected like this intothe mould cavity.

WO 04/103668 discloses a co-injection device in which a first meltstream is divided within a co-injection nozzle into two streams for theinner and outer layer. The divided streams are combined in a combinationchamber with the second melt for the middle layer upstream of anelongate central melt channel in order to form a concentrically layeredmelt stream which then is guided via the central melt channel along avalve needle to the nozzle orifice. The combination chamber is thusconfigured in a manner such that the formation of the middle layer canbe regulated with a minimum amount of material from the two streams ofthe first melt, avoiding instabilities in the flow.

EP 2 054 209 discloses a co-injection device in which a first melt isdivided into two streams upstream of the inlet into the co-injectionnozzle. The divided streams are then merged with the second melt in theregion of the nozzle tip in order to form a multilayer melt stream.

WO 11/006999 describes a co-injection device in which two melts aresupplied laterally of a co-injection nozzle, wherein the first melt isdivided within the co-injection nozzle into a stream for the inner andouter layer respectively. The streams are combined in the nozzle tip.The co-injection nozzle has a movable needle and a movable sleeve toregulate the individual melt streams.

WO 12/037682 discloses a co-injection nozzle in which a portion of afirst melt stream is guided through an annular second melt stream vialateral tunnel channels. The three melt streams are combined in theregion of the tip to form a multilayer melt stream. The inflow of themiddle melt stream can be regulated with a movable sleeve.

The material for the barrier layer is expensive, and so in multilayerinjection moulded products, it is preferably present in a layer which isas thin as possible. Furthermore, at the start and end of the respectiveinjection moulding cycle, only the first melt is injected and the meltstream for the second melt, which forms the barrier layer, isinterrupted in order to obtain an injection moulded product with acompletely encapsulated barrier layer. Precise regulation of the secondmelt is thus desirable in order to produce injection moulded productswith very thin barrier layers.

One problem which can occur with known co-injection nozzles, however, isback-flow of the second melt in the middle melt channel. If a back-flowof the second melt of this type occurs, this results in an inaccuratesupply of the second melt in the next injection moulding cycle, and thusin inaccurate or defective barrier layers for the injection mouldedproducts.

In the co-injection nozzles of WO 11/006999 and WO 12/037682, back-flowof this type can be prevented by means of a movable sleeve which canclose off the annular middle melt channel. Furthermore, the constructionof a co-injection nozzle of this type and of the co-injection device isdifficult and expensive because of the additional movable parts in theco-injection nozzle.

Other co-injection devices, such as those known from WO 00/54955 or EP 0901 896, have a back-flow control valve which is disposed outside theco-injection nozzle. EP 0 901 896 in fact concerns a co-injection nozzlewith a concentric melt outflow stream with only two layers, whereinback-flow is not so serious, because it is not suitable for theproduction of injection moulded products with a barrier layer. In WO00/54955, the back-flow control valve is disposed upstream of theco-injection nozzle in a combination unit between a front melt manifoldplate for the first melt and a rear melt manifold plate for the secondmelt.

The known co-injection nozzles with back-flow control valves—whetherthey are controlled via a movable sleeve or via an upstream back-flowcontrol valve—are of complex, multi-part construction, which isreflected in the high production and maintenance costs.

In all known co-injection nozzles with triple-layered and concentricallyconfigured outflow streams, division of the first melt and combinationof the melts to form a layered stream takes place at least in partoutside the co-injection nozzle, or they have a multi-part constructionwith many complex major components. This is particularly the case when,in addition, a back-flow control valve is provided for the second melt.

DESCRIPTION OF THE INVENTION

An object of the invention is to provide a simple and compactlyconstructed co-injection nozzle for the production of multilayerinjection moulded products with a barrier layer, wherein splitting andcombination of the melts takes place within the co-injection nozzle andwhich can be produced and maintained inexpensively. A further object isto provide a co-injection nozzle which renders a uniform disposition ofthe melt channels possible, in order to obtain a uniform distribution ofheat within the co-injection nozzle.

This object is achieved by means of the features of claim 1. Theco-injection nozzle for an injection moulding apparatus for theproduction of multilayer injection moulded products comprises a firstmelt supply channel for a first melt and a second melt supply channelfor a second melt. The two melt supply channels can simply be connectedto a supply device for the respective first and second melts.Furthermore, the co-injection nozzle comprises a central bore; anaxially movable valve needle accommodated in the central bore to openand close a nozzle orifice; an annular inner melt channel which isformed in the downstream half of the co-injection nozzle by the centralbore and the valve needle and is in fluid communication with the firstmelt supply channel; an annular middle melt channel which is in fluidcommunication with the second melt supply channel and which extendsabout the annular inner melt channel; and an annular outer melt channelwhich is in fluid communication with the first melt supply channel andwhich extends about the annular middle melt channel. The inner, middleand outer melt channels converge fluidically in the region of the nozzletip in order to form a concentrically layered melt stream. Theco-injection nozzle furthermore comprises a nozzle body and a meltdistribution insert which comprises the central bore of the co-injectionnozzle. The melt distribution insert has a circular cylinder-shapedsection with which it is accommodated in a central bore of the nozzlebody. At least one distribution channel for the first melt and at leastone distribution channel for the second melt are formed in a sleevesurface of the circular cylinder-shaped section; it primarily extends inthe axial direction.

Thus, mutually separated distribution channels for both melts can easilybe milled onto the sleeve surface of a melt distribution insert of thistype and which then is partially closed off by the inner wall of thecentral bore in the nozzle body. Bores perpendicular to the axialdirection can place the distribution channels in fluid communicationwith the central bore of the co-injection nozzle or the melt supplychannels.

The at least one distribution channel for the first melt may be inupstream fluid communication with the first melt supply channel; it canbe configured as a simple bore in the nozzle body and, if appropriate,by a flange of the melt distribution insert. Furthermore, the at leastone distribution channel may be in fluid communication with the annularinner melt channel. Downstream, it may be in fluid communication withthe annular outer melt channel.

The at least one distribution channel for the second melt may be inupstream fluid communication with the second melt supply channel anddownstream with the annular middle melt channel.

Configuring the co-injection nozzle with the melt distribution insertmeans that the at least one distribution channel for the second melt canbe connected upstream with the second melt supply channel via a meltchannel which traverses the central bore of the co-injection nozzle,wherein the traversing melt channel and the valve needle may form aback-flow barrier for the second melt. In this manner, a back-flowbarrier for the second melt is integrated into the co-injection nozzlein a simple manner without having to use further movable parts such asmovable sleeves, for example.

In one embodiment, the melt distribution insert is provided with twodistribution channels for the first melt and two distribution channelsfor the second melt. The two distribution channels for the first meltand the two distribution channels for the second melt may be distributedaround the circumference of the circular cylinder-shaped section in analternating manner and separated uniformly from each other, allowing foroptimized distribution of heat. The distribution channels may extendparallel to each other.

The distribution channels may also extend in a spiral manner in theaxial direction, so that the respective melts enter the respectiveannular melt channel in a stream which is inclined with respect to theaxis of the co-injection nozzle, and are thus distributed bettertherein.

The at least one distribution channel for the first melt may be shorterthan the at least one distribution channel for the second melt.

Furthermore, the co-injection nozzle may comprise a separating sleevethe inner wall of which forms part of the annular middle melt channeland the outer wall of which forms part of the annular outer meltchannel. The at least one distribution channel for the first melt maythus be connected downstream with the annular outer melt channel via abore in the separating sleeve.

The separating sleeve and the tip of the downstream melt distributioninsert may herein be conical in configuration, wherein the outer wall ofthe conical tip of the melt distribution insert forms part of theannular middle melt channel. Furthermore, the co-injection nozzle maycomprise a retaining and sealing sleeve which holds it on the separatingsleeve via a flange and the inner surface of which forms part of theannular outer melt channel.

The co-injection nozzle can thus easily be formed from only five maincomponents, namely a movable valve needle, a nozzle body, a meltdistribution insert, a separating sleeve, and a retaining and sealingsleeve, wherein the melt channels for splitting and distributing themelts and possibly the back-flow barrier are disposed in the meltdistribution insert. The remaining parts have just simple bores and canthus be produced as simple turned parts.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in more detail, with the aid ofexemplary embodiments and with the aid of the accompanying drawings, inwhich:

FIG. 1 shows a sectional view of a co-injection device with aco-injection nozzle in an overall view in an injection moulding mould;

FIG. 2 shows an enlarged detailed view of the co-injection nozzle ofFIG. 1;

FIG. 3 shows an exploded view of a co-injection nozzle;

FIG. 4 shows a sectional view of a co-injection nozzle without a valveneedle;

FIG. 5 shows a sectional view of the back-flow barrier;

FIG. 6 (a) to (d) shows four side views of parts of the co-injectionnozzle, in an exploded view;

FIGS. 7 (a) and (b) respectively show a sectional view of parts of theco-injection nozzle, in an exploded view; and

FIG. 8 (a) to (c) respectively show a sectional view of the co-injectionnozzle with three different positions of the valve needle.

WAYS OF CARRYING OUT THE INVENTION

FIG. 1 shows a sectional view of a hot runner co-injection device forthe production of multilayer injection moulded products provided with abarrier layer. The co-injection device comprises a mould plate 1 with arecess for a tip 9 of a co-injection nozzle 2. The co-injection nozzle 2is held in a nozzle holding plate 3. At the side opposite to the tip(i.e. upstream thereof), the co-injection nozzle 2 is provided with afirst melt supply opening 21 a to supply a first melt A through a firstmelt supply line 7 and a second melt supply opening 22 a to supply asecond melt B through a second melt supply line 8. Furthermore, a meltmanifold plate 4 is accommodated in the nozzle holding plate 3, whichdistributes the melts A, B to various co-injection nozzles 2 by means offirst and second melt supply lines 7, 8; here, only one co-injectionnozzle has been illustrated. Furthermore, a back plate 5 is provided toaccommodate the valve needle actuation device 6 for a respective valveneedle 10 of the co-injection nozzle 2.

FIG. 2 shows a detailed view of the co-injection nozzle 2 of FIG. 1(circle D). The co-injection nozzle 2 comprises four concentricallyinterengaging parts: a nozzle body 11, a melt distribution insert 12, aseparating sleeve 13, and a retaining and sealing sleeve 14. Thefour-part construction (or five-part including the valve needle 10) canalso be seen in the exploded view of FIG. 3. The nozzle body 11 may beprovided with a heating element 15.

The co-injection nozzle 2 has a central bore 20 which extends axiallythrough the melt distribution insert 12, and in which the valve needle10 is movably accommodated. In a lower section 20 a (i.e. the downstreamhalf 2 a of the co-injection nozzle 2), the central bore 20 has a largerdiameter than in the upper region 20 b (i.e. in the upstream half 2 b ofthe co-injection nozzle 2), so that an annular inner melt channel 23 isformed along the valve needle 10. The valve needle 10 may also betapered in this region, in order to increase the cross-section of theannular inner melt channel 23. In addition, only the valve needle may betapered in configuration; the central bore would then have the samediameter over its entire length. Upstream, the annular inner meltchannel 23 is in fluid communication with a first melt supply channel 21for the first melt A. Downstream, it is in fluid communication with anozzle orifice 30.

In the embodiment shown in FIG. 2, the inner melt channel 23 is taperedin the region of a conically converging tip of the melt distributioninsert 12, so that it can be closed by means of the valve needle 10. Inorder to obtain this type of taper, instead of a melt distributioninsert 12 formed in one piece, it may be provided with a screwed-on orfirmly welded conical tip.

The melt manifold plate 4 is provided with a bore 4 a through which thevalve needle 10 extends further, right up to the valve needle actuationdevice 6. The diameter of the bore 4 a of the melt manifold plate 4which is upstream of the co-injection nozzle 2 is larger than thediameter of the central bore 20 in the upper region 20 b, so that thevalve needle 10 can be guided in a contact-free manner through the meltmanifold plate 4 in order to reduce the conduction of heat via the valveneedle 10 into the melt manifold plate 4 and the back plate 5.

The first melt supply channel 21 for the first melt A is connected tothe first melt supply line 7 of the co-injection device. A second meltsupply channel 22 for the second melt B is connected to the second meltsupply line 8 of the co-injection device.

In the co-injection nozzle 2 shown, the first and second melt supplychannels 21, 22 are straight and are formed by bores in the nozzle body11 and in the melt distribution insert 12.

The first melt supply channel 21 for the melt A leads from a first meltsupply opening 21 a on the upper side of the melt distribution insert 12to the annular inner melt channel 24. At least one distribution channel26 (not shown in FIGS. 1 and 2; see FIGS. 3 and 6) for the melt A is influid communication with the first melt supply channel 21 and an annularouter channel 25, so that a melt stream A is divided into two streamswhich are respectively fed into the annular inner melt channel 24 andinto the annular outer melt channel 25. These two divided streams ofmelt form the inner and outer layers of a concentrically layered meltstream which finally passes through the nozzle orifice 30 into a mouldcavity 1 a of the mould plate 1.

The second melt supply channel 22 for the melt B leads from a secondmelt supply opening 22 a on the upper side of the melt distributioninsert 12 to a melt channel 41 traversing the central bore 20 which,together with the valve needle 10, forms a back-flow barrier 40 for thesecond melt B which is integrated into the central bore 20. In thisregard, the movable valve needle 10 in the illustrated co-injectionnozzle 2 has a recess 42 in the form of a circumferential groove orconstriction. The stream of melt through the traversing melt channel 41is blocked as a function of the position of the valve needle 10. In anopen position of the back-flow barrier 40, the recess 42 is orientatedso as to be in communication with the traversing melt channel 41, sothat the melt B can flow round the valve needle 10 in the central bore20. In a closed position which is displaced in the longitudinaldirection of the valve needle 10, the traversing melt channel 41 iscompletely closed off by the valve needle 10. The traversing meltchannel 41 is in downstream fluid communication, via at least onedistribution channel 27 (not shown in FIGS. 1 and 2; see FIGS. 3 and 6),with an annular middle melt channel 24 which extends between the annularinner melt channel 23 and the annular outer melt channel 25.

The recess 42 and the traversing melt channel 41 are therefore disposedrelative to each other in a manner such that in a first position, thevalve needle 10 closes off the nozzle orifice 30 and the traversing meltchannel 41 (see FIG. 8(a)), in a second position the nozzle orifice 30is open, while the traversing melt channel 41 is closed (see FIG. 8(b)),and in a third position both the nozzle orifice 30 and the traversingmelt channel 41 are open (see FIG. 8(c)). In the first position, neitherof the two melts A, B can flow. In the second position, only the firstmelt A can flow and the flow of the second melt B is blocked. Inaddition herein, a back-flow of the second melt B is efficientlyprevented by back-pressure of the first melt A into the middle meltchannel 24. In the third position, which corresponds to the openposition of the valve needle 10 mentioned above, the first and thesecond melts A, B can flow to the nozzle orifice 30. The recess 42 maybe in the form of a constriction, a cross-bore or a circumferential oroblique groove.

In order to form the annular middle melt channel 24 and the annularouter melt channel 25, the co-injection nozzle 2 is provided with theseparating sleeve 13 which, in the co-injection nozzle 2 shown,converges conically in the downstream direction. The inwardly orientatedsurface forms a portion of the middle melt channel 24, and the outwardlyorientated surface 25 a forms a portion of the outer melt channel 25.The inner melt channel 24 is also formed by a portion of the outersurface 24 a of the melt distribution insert 12. Furthermore, the outermelt channel 25 is formed by a portion of an inner surface of theretaining and sealing sleeve 14 which on the one hand fixes theseparating sleeve 13 in the co-injection nozzle 2, and on the other handseals the tip 9 of the co-injection nozzle 2 against the recess in themould plate 1, so that the tip 9 of the co-injection nozzle 2 or theouter surface 25 a of the separating sleeve 13 and a portion of therecess of the mould plate 1 form a front melt chamber or respectively aportion of the annular outer melt channel 25.

In the region of the nozzle tip 9, the annular inner, middle and outermelt channels 23, 24, 25 converge in order to form a concentricallylayered stream of melt which can finally be discharged through thenozzle orifice 30 into the mould cavity 1 a of the mould plate 1. Thenozzle orifice 30 can be opened or respectively closed with the movablevalve needle 10, which is provided with a tapering tip in the embodimentshown. The mould plate 1 together with the nozzle tip 9 of theco-injection nozzle 2 thus form a kind of front nozzle chamber fromwhich the melts A, B exit through the nozzle orifice 30, which lattercan be closed by the valve needle, into a mould cavity 1 a of the mouldplate 1.

FIG. 3 shows an exploded view of the co-injection nozzle 2 comprisingthe five components: valve needle 10 (only the front region which is inthe co-injection nozzle is shown), nozzle body 11, melt distributioninsert 12, separating sleeve 13 and retaining and sealing sleeve 14.FIG. 4 shows a sectional view of the co-injection nozzle 2 of FIG. 3 inthe assembled form without the valve needle and with a mould plate 1shown in diagrammatic form.

The valve needle 10 (FIG. 3) is provided with a front tapering section(in the downstream half 2 a) which, together with the central bore 20 inthe melt distribution insert 12, forms the annular inner melt channel23. Upstream (in the region of the half 2 b), the valve needle 10 has acircumferential groove or constriction 42.

The melt distribution insert 12 with the central bore 20 has an upstreamflange 50 with the first melt supply opening 21 a and the second meltsupply opening 22 a. These openings form the inlet respectively to thefirst and second melt supply channels 21, 22. A rod-shaped or circularcylinder-shaped section 51 of the melt distribution insert 12 downstreamof the flange 50 is accommodated in a central bore 52 of the nozzle body11. At the grooves formed in the sleeve surface of the section 51,distribution channels 26, 27 are formed for the melts A, B which placethe melt supply channels 21, 22 in fluid communication with the annularouter and annular middle melt channels 25, 24. The distribution channels26, 27 in this regard are partially closed by the inner wall of thecentral bore 52 in the nozzle body 11. In the upper region of thesection 51 of the melt distribution insert 12 is an incoming meltchannel 41 a and one of the two outgoing melt channels 41 b of the meltchannel 41 traversing the central bore 20. The incoming melt channel 41a is in fluid communication with the second melt supply channel 22. Theoutgoing melt channels 41 b are respectively in fluid communication withthe annular middle melt channel 24 via a distribution channel 27. In theembodiment shown, the distribution channels 26, 27 have a spiral shapein the axial direction, which allows the respective melts to enter theannular outer or inner melt channels 25, 24 at an inclination withrespect to the axial direction, in order to obtain better distributionof the melt (see also FIG. 6).

FIG. 5 shows a detailed sectional view of the integrated back-flowbarrier 40. The melt channel 41 traversing the central bore 20 is formedby an incoming melt channel 41 a and two outgoing melt channels 41 b.These are formed by lateral bores in the rod-shaped or circularcylinder-shaped section 51 of the melt distribution insert 12 whichreach right into the central bore 20. The bore in the nozzle body 11 forthe second melt supply channel 22 reaches right to the bore for theincoming melt channel 41 a. The valve needle 10 with the recess 42 isaxially movably accommodated in the central bore 20. The back-flowbarrier in FIG. 5 is shown in the open position, and the melt B can passunhindered through the back-flow barrier.

Furthermore, the separating sleeve 13 and the retaining and sealingsleeve 14 seen in FIG. 3 and FIG. 4, as already described, form theannular middle melt channel 24 and the annular outer melt channel 25together with the melt distribution insert 12. A conical tip of therod-shaped section 51 of the melt distribution insert 12 is accommodatedherein at a distance from the conical separating sleeve 13. The tip ofthe conical separating sleeve 13 is accommodated herein, at a distancefrom the retaining and sealing sleeve 14. The retaining and sealingsleeve 14 has been screwed firmly into the nozzle body 11 and thus holdsthe separating sleeve 13 in the co-injection nozzle 2. For this purpose,the separating sleeve 13 may be provided with a flange at its upstreamend. The melt distribution insert 12 is screwed onto the nozzle body 11via its flange 50. To clean the co-injection nozzle 2, this can easilybe removed from the nozzle holding plate 3 and the mould plate 1 and bebroken down into its individual parts.

A particular advantage of the construction of the co-injection nozzlewith the melt distribution insert described lies in the fact that theintegrated back-flow barrier and the distribution of the two meltswithin the co-injection nozzle can easily be obtained by a few bores andmilled grooves in the melt distribution insert.

In the co-injection nozzle 2 shown in FIGS. 3 and 4, the separatingsleeve 13 is provided with an opening 13 a the diameter of whichcorresponds to the diameter of the tapered valve needle 10. In thismanner, the valve needle 10 can take a position in which the fluidcommunication of the annular inner and middle melt channels 23, 24 withthe nozzle orifice 30 is interrupted. The opening 13 a may also,however, have the same diameter as the lower section 20 a of the centralbore 20.

FIG. 6 shows four side views: FIGS. 6(a) to 6(d) (front, right, back,left) of the melt distribution insert 12 and the separating sleeve 13 inan exploded view, wherein the views are respectively rotated by 90°.FIG. 7(a) (right, see FIG. 6(b)) and FIG. 7(b) (front, see FIG. 6(a))respectively show a sectional view of the melt distribution insert 12and the separation sleeve 13 in an exploded view.

The spiral shape of the distribution channels 26, 27 can be seenparticularly well in FIG. 6. In the embodiment of the melt distributioninsert 12 shown, for the first and the second melts A, B, twodistribution channels 26, 27 are respectively formed. The twodistribution channels 26 for the first melt A and the two distributionchannels 27 for the second melt B alternate and are at a uniformdistance from each other around the circumference of the circularcylinder-shaped section 51, allowing for optimized distribution of heatwithin the co-injection nozzle 2. In similar manner, the distributionchannels may also be formed so as to run straight in the axialdirection.

The incoming melt channel 41 a of the back-flow barrier can be seen inFIG. 6(b). In the central bore 20 of the melt distribution insert 12,the second melt B is divided into two streams which pass through theoutgoing melt channels 41 b (FIGS. 6(a) and 6(c)) into the respectivedistribution channels 27.

The first melt supply channel 21 reaches right up to the central bore 20of the melt distribution insert 12 (FIG. 7(b)). In this region, aportion of the melt A is guided laterally in two distribution channels26 on the surface of the melt distribution insert 12 and a portion isguided into the annular inner melt channel 23 along the lower section 20a of the central bore 20. The first distribution channel 26 is feddirectly through the first melt supply channel 21. A connecting channel28 connects the second distribution channel 26 to the central bore 20,and thus is supplied with the first melt A.

The distribution channels 27 start upstream of the distribution channels26 and extend further downstream than the distribution channels 26, intothe region of the annular middle melt channel 24, part of which isformed by the surface 4 a of the conical tip of the melt distributioninsert 12. The distribution channels 26 for the first melt A are thusshorter in length than the distribution channels 27 for the second meltB.

The annular outer melt channel 25 extends in the axial direction furtherupstream than the annular middle melt channel 24. In this manner, thedistribution channel 26 can feed the annular outer melt channel 25through a bore 26 a in the separating sleeve 13 without having totraverse the middle melt channel 24. This bore 26 a ends in the outersurface 25 a of the separating sleeve 13, which forms part of theannular outer melt channel 25.

In all of the figures, the same reference numerals are used for the sameparts.

REFERENCE LIST

-   1 mould plate-   1 a mould chamber (cavity)-   2 co-injection nozzle-   2 a half of co-injection nozzle (downstream)-   2 b half of co-injection nozzle (upstream)-   3 nozzle holding plate-   4 melt manifold plate-   4 a bore-   5 back plate-   6 valve needle actuation device-   7 first melt supply line-   8 second melt supply line-   9 nozzle tip-   10 valve needle-   11 nozzle body-   12 melt distribution insert-   13 separating sleeve-   14 retaining and sealing sleeve-   15 heating element-   20 central bore-   20 a lower section of central bore-   20 b upper section of central bore-   21 first melt supply channel-   21 a first melt supply opening-   22 second melt supply channel-   22 a second melt supply opening-   23 annular inner melt channel-   24 annular middle melt channel-   25 annular outer melt channel-   26 distribution channel for melt A-   26 a bore-   27 distribution channel for melt B-   28 connecting channel-   30 nozzle orifice-   40 back-flow barrier-   41 traversing melt channel-   41 a incoming melt channel-   41 b outgoing melt channel-   42 recess-   50 flange-   51 rod-shaped/circular cylinder-shaped section-   52 central bore of nozzle body-   A first melt-   B second melt

The invention claimed is:
 1. A co-injection nozzle for an injectionmoulding device for the production of multilayer injection mouldedproducts from a multilayer injection, the nozzle comprising: a nozzlebody forming a body central bore; a melt distribution insert(hereinafter “insert”): (a) forming an insert central bore, (b) inmutual contact with the nozzle body along an upstream portion of anaxial length of the insert, (c) defining a longitudinal axis having anupstream end and a downstream end at an opposite end of the longitudinalaxis relative to the upstream end, and (d) having a circularcylinder-shaped end profile located at the downstream end; a circularshaped lower separating sleeve positioned to surround the insert alongthe longitudinal axis of the insert at the downstream end; a nozzleorifice positioned proximate the downstream end of the insert and fromwhich the multilayer injection is output from the co-injection nozzle; afirst melt supply channel for a first melt; a second melt supply channelfor a second melt; an axially movable valve needle accommodated in theinsert central bore to open and close the nozzle orifice; an annularinner melt channel which is formed between the insert central bore andthe valve needle and being in fluid communication with the first meltsupply channel; an annular middle melt channel which is in fluidcommunication with the second melt supply channel and which extendsabout the annular inner melt channel between the circular shaped lowerseparating sleeve and an exterior surface of the insert along thelongitudinal axis of the insert at the downstream end of the insert; anannular outer melt channel which is in fluid communication with thefirst melt supply channel and which extends about the annular middlemelt channel at the downstream end of the insert; the inner, middle andouter melt channels converging fluidically in the region of the nozzleorifice to form a concentrically layered melt stream; and at least onedistribution channel for the first melt and at least one distributionchannel for the second melt each being formed as a groove in the surfaceof the circular cylinder-shaped end profile of the insert.
 2. Theco-injection nozzle of claim 1, wherein the at least one distributionchannel for the first melt is in upstream fluid communication with thefirst melt supply channel and with the annular inner melt channel, andin downstream fluid communication with the annular outer melt channel.3. The co-injection nozzle of claim 1, wherein at least one distributionchannel for the second melt is in upstream fluid communication with thesecond melt supply channel and downstream with the annular middle meltchannel.
 4. The co-injection nozzle of claim 1, wherein the at least onedistribution channel for the second melt is connected upstream with thesecond melt supply channel via a melt channel which traverses the insertcentral bore of the co-injection nozzle, wherein the traversing meltchannel and the valve needle form a back-flow barrier for the secondmelt.
 5. The co-injection nozzle of claim 1, wherein the insert isprovided with two distribution channels for the first melt and twodistribution channels for the second melt.
 6. The co-injection nozzle ofclaim 5, wherein the two distribution channels for the first melt andthe two distribution channels for the second melt are distributed aroundthe circumference of the circular cylinder-shaped section in analternating manner and separated uniformly from each other.
 7. Theco-injection nozzle of claim 1, wherein the distribution channels extendparallel to each other.
 8. The co-injection nozzle of claim 1, whereinthe distribution channels extend in a spiral manner in the axialdirection.
 9. The co-injection nozzle of claim 1, wherein the at leastone distribution channel for the first melt is shorter than the at leastone distribution channel for the second melt.
 10. A co-injection nozzlefor an injection moulding device for the production of multilayerinjection moulded products from a multilayer injection, the nozzlecomprising: a nozzle body forming a body central bore; a meltdistribution insert (hereinafter “insert”): (a) forming an insertcentral bore, (b) in mutual contact with the nozzle body along anupstream portion of an axial length of the insert, (c) defining alongitudinal axis having an upstream end and a downstream end at anopposite end of the longitudinal axis relative to the upstream end, and(d) having a circular cylinder-shaped end profile located at thedownstream end; a circular shaped lower separating sleeve positioned tosurround the insert along the longitudinal axis of the insert at thedownstream end; a nozzle orifice positioned proximate the downstream endof the insert and from which the multilayer injection is output from theco-injection nozzle; a first melt supply channel for a first melt; asecond melt supply channel for a second melt; an axially movable valveneedle accommodated in the insert central bore to open and close thenozzle orifice; an annular inner melt channel which is formed betweenthe insert central bore and the valve needle and being in fluidcommunication with the first melt supply channel; an annular middle meltchannel which is in fluid communication with the second melt supplychannel and which extends about the annular inner melt channel betweenthe circular shaped lower separating sleeve and an exterior surface ofthe insert along the longitudinal axis of the insert at the downstreamend of the insert; an annular outer melt channel which is in fluidcommunication with the first melt supply channel and which extends aboutthe annular middle melt channel at the downstream end of the insert; theinner, middle and outer melt channels converging fluidically in theregion of the nozzle orifice to form a concentrically layered meltstream; and at least one distribution channel for the first melt and atleast one distribution channel for the second melt being formed in thesurface of the circular cylinder-shaped end profile of the insert;wherein the separating sleeve includes an inner surface of which formspart of the annular middle melt channel and an outer surface of whichforms part of the annular outer melt channel.
 11. A co-injection nozzlefor an injection moulding device for the production of multilayerinjection moulded products from a multilayer injection, the nozzlecomprising: a nozzle body forming a body central bore; a meltdistribution insert (hereinafter “insert”): (a) forming an insertcentral bore, (b) in mutual contact with the nozzle body along anupstream portion of an axial length of the insert, (c) defining alongitudinal axis having an upstream end and a downstream end at anopposite end of the longitudinal axis relative to the upstream end, and(d) having a circular cylinder-shaped end profile located at thedownstream end; a circular shaped lower separating sleeve positioned tosurround the insert along the longitudinal axis of the insert at thedownstream end; a nozzle orifice positioned proximate the downstream endof the insert and from which the multilayer injection is output from theco-injection nozzle; a first melt supply channel for a first melt; asecond melt supply channel for a second melt; an axially movable valveneedle accommodated in the insert central bore to open and close thenozzle orifice; an annular inner melt channel which is formed betweenthe insert central bore and the valve needle and being in fluidcommunication with the first melt supply channel; an annular middle meltchannel which is in fluid communication with the second melt supplychannel and which extends about the annular inner melt channel betweenthe circular shaped lower separating sleeve and an exterior surface ofthe insert along the longitudinal axis of the insert at the downstreamend of the insert; an annular outer melt channel which is in fluidcommunication with the first melt supply channel and which extends aboutthe annular middle melt channel at the downstream end of the insert; theinner, middle and outer melt channels converging fluidically in theregion of the nozzle orifice to form a concentrically layered meltstream; and at least one distribution channel for the first melt and atleast one distribution channel for the second melt being formed in thesurface of the circular cylinder-shaped end profile of the insert;wherein the at least one distribution channel for the first melt isconnected downstream with the annular outer melt channel via a bore inthe separating sleeve.